• Sheng Yang's avatar
    KVM: Enable MSI-X for KVM assigned device · d510d6cc
    Sheng Yang authored
    This patch finally enable MSI-X.
    
    What we need for MSI-X:
    1. Intercept one page in MMIO region of device. So that we can get guest desired
    MSI-X table and set up the real one. Now this have been done by guest, and
    transfer to kernel using ioctl KVM_SET_MSIX_NR and KVM_SET_MSIX_ENTRY.
    
    2. Information for incoming interrupt. Now one device can have more than one
    interrupt, and they are all handled by one workqueue structure. So we need to
    identify them. The previous patch enable gsi_msg_pending_bitmap get this done.
    
    3. Mapping from host IRQ to guest gsi as well as guest gsi to real MSI/MSI-X
    message address/data. We used same entry number for the host and guest here, so
    that it's easy to find the correlated guest gsi.
    
    What we lack for now:
    1. The PCI spec said nothing can existed with MSI-X table in the same page of
    MMIO region, except pending bits. The patch ignore pending bits as the first
    step (so they are always 0 - no pending).
    
    2. The PCI spec allowed to change MSI-X table dynamically. That means, the OS
    can enable MSI-X, then mask one MSI-X entry, modify it, and unmask it. The patch
    didn't support this, and Linux also don't work in this way.
    
    3. The patch didn't implement MSI-X mask all and mask single entry. I would
    implement the former in driver/pci/msi.c later. And for single entry, userspace
    should have reposibility to handle it.
    Signed-off-by: default avatarSheng Yang <sheng@linux.intel.com>
    Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
    d510d6cc
kvm_main.c 59.2 KB